1. Field of the Invention
The present invention relates to a color filter and a cathode-ray tube using the color filter.
2. Description of the Related Art
As examples of a color filter having an inorganic substrate, there are known a color filter having a color layer obtained by diffusing metallic ions in a glass plate, and a color filter formed by printing a dye on a glass plate. In the case of the former, however, the hue of the color filter cannot be freely selected because of the use of metal ions. Also, in the case of the latter, it is difficult to effect printing on the surface of an inorganic substrate.
Japanese Patent Publication No. 58-17134 discloses a method wherein an aluminum layer is deposited on an inorganic substrate, the aluminum layer is oxidized to obtain a transparent aluminum oxide layer, and the aluminum oxide layer is colored with a dye or the like, thus forming a color layer. In this method, an expensive deposition apparatus is required for the deposition of aluminum. Thus, the cost for manufacturing the color layer increases. The deposition device becomes more expensive, as the size of the substrate, on which aluminum is to be deposited, increases. In addition, since the refractive index of aluminum oxide is high, the formation of an aluminum oxide layer on the surface of a glass plate, etc., increases the reflectivity of the resulting body and the transparency of the body decreases. Furthermore, since the light resistance of the color layer colored with a dye is low, the color of the dye on the surface of the aluminum oxide layer may be faded by direct irradiation of solar light.